Keeping the original file date and time is just simply wrong, and actually causes problems.
When you encrypt a file, it is transformed into something else. It’s not the same file. It should have the date and time of the transformation.
When you decrypt a file, it will have it’s date and time restored, since then the file is back to it’s original form and then it makes sense to restore the date and time as well the file name etc.
The problems caused include backup and synchronization software stopping to work. Many such softwares have “last time run” marker, and will only examine files that are newer. If we made encrypted files have the original un-encrypted file date and time, this strategy stops working. It has happened. There are other issues too.
Finally, we are encrypting files i.e. hiding information from view, and allow you to rename the encrypted file names as well. If we kept the original date and time, that would leak a little bit of information about the original file.
But, mostly, it’s just fundamentally wrong to transform a file and keep the original date and time of change. It’s changed. So its timestamp should change. If the information inside is unchanged (which it is in this case), that should be kept in meta data inside the file (which AxCrypt does).